For reliability improvement, cost reduction, and reduction of development time, an electric vehicle may be equipped with a power unit constructed of an electric motor and other parts and a battery unit serving as a power source, using a vehicle body of the vehicle which is designed to be equipped with an internal combustion engine. More specifically, an engine room that is formed on one end side of the vehicle body as considered in a longitudinal direction of the vehicle body is utilized without change as a power unit room for installing the power unit. The battery unit is set under the floor of a passenger compartment situated in the center of the vehicle body.
In general, the power unit of an electric vehicle is supported onto the frame of the power unit room by means of a first bracket protruding sideways from the battery unit-side end of the power unit and a second bracket protruding sideways from the opposite end of the power unit, as disclosed in Unexamined Japanese Patent Publication No. 8-310252 (hereinafter, referred to as Patent Document 1). To be more concrete, both ends of the first bracket and those of the second bracket are supported onto the frame of the power unit room, and the first and second brackets support the power unit at their more internal positions than their ends.
In the case of an electric vehicle of this type, it is easy to secure a space for installing devices in the central region and ends of the vehicle body as described above. For a reason related to construction, therefore, the power unit and the batter unit are likely to be installed alongside of each other in the vehicle body. The mileage of the electric vehicle is determined considerably by electric capacity of the battery installed, so that there is a demand to install as large a battery as possible. It is then difficult to save a wide space between the power and battery units that are adjacently arranged in the vehicle body.
If the electric vehicle crashes on the side where the power unit is installed (first side), and an impact load is entered from the first side of the vehicle body, only the vehicle body is forcibly displaced, leaving the power unit behind, in the direction of the battery unit that is positioned closer to the center of the vehicle body than the power unit is. In result, the power unit is pushed out towards the battery unit since it is supported onto the vehicle body by the first and second brackets. However, as the space between the power and battery units is small, if the power unit is pushed out without resistance along with the displacement of the vehicle body, the power unit smashes against the end of the battery unit, and the battery unit might be damaged.
At this time point, the stress produced by relative displacement between the vehicle body and the power unit is concentrated in the first and second brackets at their central regions, the spans of which are relatively large. In case that the first and second brackets are broken at their central regions, a force causing the relative displacement of the power unit towards the battery unit is suppressed.
The broken first and second brackets, however, are still connected to the power unit. For this reason, especially as to the first bracket located on the battery unit side, a sharp fractured part of the bracket portion that has been broken at the central region might hit against the end of the battery unit and damage the battery unit.
In the field of vehicles, one possible idea to deal with the above situation is to form a fragile portion in the first bracket so that the battery unit-side bracket is broken at a certain position. In the case of the electric vehicle, however, simply forming the fragile portion is no guarantee that the battery unit will be protected from the damage described above.
This is because the impact-related behavior of the electric vehicle on the side where the power unit is not installed (second side) is different from that on the side where the power unit is installed (first side). In contrast to the situation where an impact is applied to the first side, if an impact load is entered from the second side of the vehicle body due to a collision with the second side, the power unit is forcibly displaced in the direction of the battery unit due to inertia of the power unit. The first bracket in this situation, unlike the situation where the impact is applied, to the first side, is required to avoid a breakage in the bracket as much as possible and to prohibit a relative approach of the power unit to the battery unit.
However, the first bracket rather becomes easily broken even at the time of collision with the second side where the power unit is not installed, if the fragile portion is merely formed in the first bracket. Consequently, at the time of collision with the second side where the power unit is not installed, the power unit is likely to hit against and damage the battery unit.